Hydraulic circuit



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HYDRAULIC CIRCUIT Filed Feb. 27, 1941 5 Sheets-Sheet 5 INVENTOR @fm/AMCa/s av J, a

ATTORNEYS Patented Dec. 236, 1944 HYDRAULIC cmcurr nunk w. curan,springfield, Mssg., minor to Van Norman Company, a corporation ofMassachusetts Application February 27, 1941,'Serial No. 380,897

l Claims. (Cl. 60-52) This'invention relates to a hydraulic circuit andacontrol therefor, particularly adapted for machine tools such as miningmachines.

Many forms of hydraulic controlling mech-- anisms have heretofore beenproposed, and it is one object of the present invention to simplifythese controlling mechanisms. It is a further object to construct avalve mechanism capable of giving feed and rapid traverse motion in onedirection and rapid traverse motion in the reverse direction, and toregulate the speed by an adjustable throttle, preferablyA in the outlet,which is by-passed in order to secure rapid traverse. It is a furtherobject to improve and simplify the hydraulic mechanism for shifting thecontrol valve into reversing position. It is a further object to providea simple and effective way of inverting the cycle of operation of themachine. Additional objects will appear from the following descriptionand claims.

Referring to the drawings,

Fig. l is a diagrammatic view of the circuit;

Figs. 2 and 3 are diagrams showing two cycles obtained from the controlmechanism by means of 'the cycle inverter;-

Fig. 4 is a diagrammatic view of the control valve mechanism vinposition to impart rapid traverse in a forward direction, the cycleinvert- Fig. 8 is a detail of a valve for controlling the spindleclutch.

Thevalve mechanism is intended in particular for operation with ahydraulic circuit such as is 4shown in Fig. l. A pipe leads from an oilsump' to a pump |2 which may be of any desired design but which ispreferably of the constant delivery type. A relief valve I3 connected inthe output pipe |4 of the pump has alconnection I5 leading back to thesump and functions in the usual manner to permit excess oil to pass outof the line I4 and to hold the pressure in that line substantiallyconstant. The line |4 extends to a panel box lliY which is preferablyconstructed mechanically in accordance with my copending applicationSerial No. 396,857, led June 6, 1941, now Patent No. 2,308,647. Thehydraulic 'features of the panel are shown in Figs. 4 to 7, and includea valve casing in which is a spool valve I8 of novel construction.

From the valve casing l1 extend several conduits arranged sequentiallyin the following order. At one end of the series is the fluid pressurepipe I4, leading into an annular chamber or port 26. An adjacent chamberI9 is separated from chamber 26 by an inwardly projecting rib 20. Aconduit 2| leads from the chamber I9 to one end of the operatingcylinder 22, preferably through a cycle-inverting four-way valve 23 anda conduit 24 as shown on Fig. l. A third chamber 25, separated fromchamber I9 by a rib 21. is connected to the sump by a pipe 31. Thechamber 25 is of about twice the length of chambers 26 and I9 to permitit to be connected either to chamber i9 or to the next chamber 28 fromwhich it is separated by a rib 23. This latter chamber is connected by apipe 30 to the casing of a throttle valve 3| which may be of any desiredtype but is preferably formed as a rotating cylinder having a helicalgroove as is fully set forth in my copending application Serial No.381,780

4iiled Mar. 5, 1941. A conduit 32 leads from this throttle to thefour-way valve 23 (Fig. 1) and a pipe .33 from that valve to the secondend of the cylinder. As previously stated, the cycle inverter 23 hasbeen omitted from Figs. 4 to 7 for clearness, the pipe 32 being showncoupled directly to the cylinder 22. A fth chamber 34, separated fromchamber 28 by a rib 35, is coupled by a conduit 36 with the conduit 32previously mentioned.

'I'he spool valve I8 has a head 38 at one end positioned adjacent theend 33 of casing Il so as to form a chamber 4|! into which pressurefluid may be introduced to shift the spool as will be described below.Next to this is an annular channel 4| positioned so as not to makeconnection with any of the chambers except in the reversing position 0fthe spool. Separated from channel 4| by a rib 42 is a channel 43 ofsubstantially greater length. A wide rib 44 then intervenes, beingfollowed by channels 45 and 4B which in most positions of the valve actas a single channel of considerable length, but which for certainpurposes are separated into two channels by a rib 41.

Cylinder 22 is preferably stationary in order to avoid the necessity ofmaking hydraulic connections to a moving cylinder, the rod of its piston5| being connected to the reciprocating table I8 is set to cause thepressure fluid to enter at the right of the piston and the liquid fromthe left of the piston is forced out directly tothe sum Tllijere is noprovision made in the spool valve for motion at a feed rate during thereturn stroke of the table, as the elimination of this extra capabilitygreatly reduces the complexity of the spool yalve mechanism. To allowthe cycle to be inverted the four-way valve 23 is provided. It should beunderstood that this valve does not act as a reversing valve duringnormal operation of the machine, the spool valve I8 performing thisfunction. The four-way valve is used only when it is desired to have thecycle of operation start from the other end. of the table (compare Figs.2 and 3), and can be `built into the base of the machine in a relativelyinaccessible position where it will not complicate the controls whichare used during normal operation.

The several operative positions of the spool valve are shown in Figs. 4to 7 inclusive. Fig. 4 shows the valve in position to cause rapidtraverse movement in a forward direction. In this and succeeding figuresthe cycle inverting valve has been omitted, as it merely changes thedirection of movement of the table without affecting in any way theoperation of the remaining parts. To obtain rapid forward movement thespool valve I8 is located in its position nearest to the head 39 of thecasing I1. In this position channel 43 joins the chambers 26 and I9,thus connecting the pipes I4 and 2| and admitting fluid under pressureto the left hand end of the cylinder 22. Channels 45 and 46 in this caseact as a single long channel joining the chambers 25, 28, and 34, therib 41 lying within the chamber 28 and being ineffective as a dividingWall. It should be noted that the return line from cylinder 22 in theorybranches from pipe 32 either through pipe 36 or through the throttle 3l,uniting again in the valve casing and extending to the sump through theline 31. The amount of ow through the throttle is in this casenegligible and unimportant since the direct path through pipe 86 offersso much less resistance. The use of the two lines in parallel, however,is of advantage as it simplifies the valve construction.

In Fig. 5 the pressure uid line to. the cylinder is left unchanged, butthe rib 41 is moved into line with the rib 35 so as to shut oi thechamber 34 and force all the liquid through the throttle 3l. The tablewill in this case be moved forwardly at a speed determined by thesetting of the throttle;` which, if the throttle is constructed inaccordance with my application Serial No. 381,780 can be regulated withgreat accuracy.

In Fig. 6 the spool has been moved one step further to the right, sothat the conduits I4 and 31 are directly connected together. Thepressure fluid is thus vented directly to the sump, and no movement ofthe table takes place.

The final position is shown in Fig. 'l and shows the spool moved to itsright hand position. giving a reverse motion to the table at high speed.The rib 42 has here been brought adjacent the ri-b 20, shutting offchamber 26 from chamber I9 and retaining the pressure fluid within thechamber 4I, which for the first time comes into separate operation. Thischamber is connected with. chamber 45 by a duct 55 extending within andcentrally of the spool. Through this duct pressure fluid passes into thejoint chambers 28 and 34 and thence to the right hand end of thecylinder through conduits 36 and 32. Here again the throttle isineffective on account of the lower resistance of the other path, andthe liquid passes freely to the cylinder. Liquid forced out from theother end of the cylinder is passed through `the chambers I9 and 25 tothe discharge line 31.

For manual control of the spool valve the spool is provided with anintegral rack 56 (Fig. 4) meshing with a wide gear 51. A second rack 58also meshes with this gear, and at its upper end carries a, roll 59engaged by suitable dogs 66 on the table. By suitably proportioning thedogs the spool may be shifted between its feed and rapid traverseadvance positions, or from either of these positions tothe stopposition. The spool is centralized and releasably held in any of itspositions by a spring pressed detent 6I engaging notches 62 in thespool.

The mechanical shifting mechanism described is capable of changing thespeed of and stopping the table, but it cannot cause reversal because inorder to place the spool in its reversing position it is necessary topass through its stopping position. Once the table is stopped there isof course no movement of the dogs to cause further shifting of thespool. To shift the spool into reversing position pressure fluid isintroduced into chamber 40 through a pipe 63 under the control of aspool valve 64 in a, casing 65. The casing has three spaced chambers 66,61, and 68 connected respectively to a line `95 leading to the pressureline I4, the pipe 63', and a line 69 leading to the sump. The spool hastwo recesses'10 and 1I which, when the spool is in its normal vpositionof Fig. 4, straddle the chambers 61 and 68 and keep the chamber 40connected to the sump. When the valve is depressed as in Fig. 7 therecesses 10 and 1I straddle the chambers 66 and 61 and admit pressurefluid from line I4 to chamber 40, causing the spool valve I8 to beshifted all the way to the right without pausing at the stop position.The spool 64 is returned to normal by a spring 12 as soon as thereversing dog 13 on the table has left the stem 14 of the valve. Asshown in Fig. l, the operating stems 58 and 14 of the two spool valvesare located near the center of travel of the table (preferably closertogether than shown) and may -be actuated by dogs lying in differentplanes to avoid interference.

The normal cycle of the machine is rapid advance to the neighborhood ofthe work, then slow advance at a rate determined by the throttlesetting. a rapid return, and stoppage. The starting is brought about bymanual shifting of spool valve I8 by a handle 15 on gear 51. The spoolis shifted from rapid traverse to feed position by a dog 60, and then isshifted to its rapid traverse reverse position hydraulically by theshifting of spool 64 by dog 13. Stoppage at the initial position of thetable is brought about by a dog 16 having the usual ledge to underlieroll 59 and raise plunger 58 to move spool I8 from the position of Fig.'1 to that of Fig. 6. If it is desired to have the feed in the oppositedirection the cycle inverting valve 23 is manually changed, whereuponthe automatic cycling control proceeds as before but with the directionsreversed.

If it is desired to use the circuit described for throwing out thespindle control clutch of the machine tool while the table is travelingat rapid traverse, this is preferably done by a servo-motor acting onthe clutch 82 through any suitable linkage 83. The servo-motor issupplied with fluid by a sequence valve 84 inserted in the line 2l andshown in detail in Fig. 8. This valve may be of various forms, thatshownbeing illustrative and diagrammatic only. Basically it consists ofa casing B into which the line 2| opens on opposite sides. A pistonvalve 86 slides within the casing, and is normally held at one endthereof by a spring 81. A'central constriction 88 in the valve .permitsfluid to flow freely at all times between the two branches of the line2|. When the valve I8 is set to cause rapid traverse movement of thetable in either direction, the throttle 3| is Icy-passed, and there is`but slight resistance to the passage of vfluid through line 2|. When thespool valve is shifted to its feed rate position, however, the fluidexhausted from the cylinder 22 has to pass through the throttle, and thepressure in the line 2| rises sharply. As this occurs the valve 86 willbe shifted against the action of its spring by fluid passing through aduct 89, causing the piston to uncover a port 90 connected to theservo-motor by a line 9|'. As long as the main valve is set at feed ratethe spindle clutch will remain in engagement, returning to inactiveposition as soon as the circuit is shifted to stop or to rapid traversein either direction. A check valve 92 permits the fluid in theservo-motor to drain back to the line as soon as the pressure in thelatter drops.

It is sometimes desirable to operate a workclamp hydraulically. Such aclamp is shown conventionally in Fig.,l, operated by a servomotor ethaving conduits 91, 93 leading through a four-way valve 99 to the line95 and to the sump. By shifting the valve manually or automatically theclamp may be placed in either active or inactive position. To free theclamp servomotor from the sudden drop in pressure resulting when thecircuit is in stop or rapid traverse condition, it is preferable toplace a loading Valve |00 in the line i4, and to take oil the line S5between it and the pump. This loading valve may be of any desiredconstruction, and operates to keep a pressure of say 50 lbs. per squareinch at all times in the line 95. On the feed stroke the pressure mayrise to that for which the relief valve I3 is setl (say 200 lbs.), butcan never fall below the pressure determined by the loading valve.

What I claim is:

l. A hydraulic circuit for causing reciprocatory motion of a machineelement comprising a cylinder` and a piston one of which is stationaryand the other connected to said element, a sump, a source of liquidunder pressure, and means for controlling the flow of liquid to andfromV the cylinder comprising a spool valve and a cooperating valvecasing, said casing having in sequential relation a pressure fluidinlet, a connection to one -end of the cylinder, a connection to thesump, a connection through a throttle to the second end of the cylinder,and a connection around the throttle valve to said second end of thecylinder, the valve casing and spool being relatively so formed thatwith the `valve at one extreme position the fluid inlet is coupled tothe first end of the cylinder and shut off from the sump and the secondend of the cylinder is connected directly to the sump, in a secondposition the uid inlet connection is unchanged and the i second end ofthe cylinder is connected to the sump through the throttle valve only,in a third position the fluid inlet is connected to the sump, and in afourth position the uid inlet is connected directly to the second end ofthe cylinder and the rst end of the cylinder is connected to the sump.

2. A hydraulic circuit for causing reciprocatory motion of a machineelement comprising a cylinder and a piston one of which is stationaryand the other connected to said element, a sump, a source of liquidunder pressure, and means for controlling the ow of liquid to andfromthe cylinder comprising aspool valve and a cooperating valve casing,said casing having in se-v quential relation a pressure uid inlet, aconnection to one end of the cylinder, a connection to the sump, aconnection through a throttle to the second end of the cylinder, and aconnection around the throttle valve to said second end of the cylinder,the valve spool being providedwith a circumferential depression ofsufficient length to straddle the rst three of said connections, asecond circumferential depression of sufficient length and suitablypositioned to straddle the last three of said connections when the spoolis in either one of two positions in which the first depressionstraddles the first two connections only, a barrier in said seconddepression positioned to separate the last twoconnections when the spoolis in one of said latter positions, and a third depression connectedinternally of the spool with the second depression and positioned toconnect with the first connection when the spool is in position for therst depression to couple the second and third connections only.

3. A hydraulic circuit for causing reciprocatory motion of a machineelement comprising a cylinder and a piston one of which is stationaryand the other connected to said element, a sump, a source of liquidunder pressure, and means for controlling the flow of liquid to and fromthe cylinder comprising a spool valve and a cooperating valve casing,said casing having in sequential relation a pressure fluid inlet, aconnection to one end of the cylinder, a connection to the sump, aconnection through a throttle to the second end of the cylinder, and aconnection around the throttle valve to said second end of the cylinder,the valve casing and spool-being relatively so formed that with thevalve yat one extreme position the fluid inlet is coupled to the firstend ofthe cylinder and shut off from the sump and the second end of thecylinder is connected directly to the sump, in a second position thefluid inlet connection is unchanged and the second end of the cylinderis connected to the sump through the throttle valve only, in a thirdposition the fluid inlet is connected to the sump, and in a fourthposition the fluid inlet is connected directly to the second end of thecylinder and the rst end of the cylinder' is connected to the sump,mechanical means for shifting the spool into any of said positions, andhydraulic meansfor shifting the spool into said fourth position.

d. A hydraulic circuit for causing reciprocatory motion of a machineelement comprising a cylinder and a piston one of which is stationaryand the other connected to said element, a sump, a source of liquidunder pressure, and means for controlling the flow of liquid to and fromthe cylinder comprising a spool valve and a cooperating valve casing,said casing having in sequential relation a pressure fluid inlet, aconnection to one end of the cylinder, a connection to the sump, aconnection through a throttle to the second end of the cylinder, and aconnection around the throttle valve to said second end of the cylinder,the valve spool being provided With a circumferential depression ofsufcient length to straddle the first three of said connections, a,second circumferential depression of suillcient length and suitablypositioned to straddle the last three of said connections when the spoolis in either one of two positions in which the ilrst depressionstraddles the first two connections only, a barrier in said seconddepression positioned to separate the last two connections when thespool is in one of said latter positions, and a third depressionconnected internally ofthe spool with the second depression andpositioned to connect with the rst connection when the spool is inposition for the ilrst depression to couple the second and thirdconnections only, mechanical means for shifting the spool into any ofsaid positions, and hydraulic means for shifting the spool into saidfourth position.

5. A hydraulic circuit for causing reciprocatory motion of a machineelement comprising a cylinder and a piston one of which is stationaryand the other of which is connected to said Aelement, a source lofliquid under pressure, a sump, a throttle, a valve casing having in theorder named a first port connected to the source, a second portconnected to one end of the cylinder, a third port connected to thesump, a fourth port connected to the second end of the cylinder throughthe throttle, and a fifth port connected to the second end of thecylinder exclusive of the throttle, and a spool valve within the casinghaving a groove connecting theA second port alternatively with the firstand third ports or with both together, a second groove connecting thethird port with the fourth and fifth ports, said second groove having anintermediate circumferential rib separating the fourth and fth ports inlone position of the spool, and a third groove connected by an internalbore with the second groove and alignable with the first port.

6. A hydraulic circuit for causing reciprocatory motion of a machineelement comprising a cylinder and a piston one of which is stationaryand the other of which is connected to said element, a source of liquidunder pressure, a sump. a throttle, a valve casing having in the ordernamed a first port connected to the source, a second port connected toone end of the cylinder, a third port connected to the sump, a fourthport connected to the second end of the cylinder through the throttle,and a flfth port connected to the second end of the cylinder exclusiveof the throttle, and a spool valve within the casing having a grooveconnecting the second port alternatively with the ilrst and third portsor with both together, a second groove connecting the third port withthe fourth and fifth ports, said second groove having an intermediatecircumferential rib separating the fourth and fifth ports in oneposition of the spool, a third groove connected by an internal bore withthe second groove and alignable with the first port, mechanical meansengaging one end of the valve to shift it, and hydraulic means engagingthe other end of the valve to shift it in one direction.

7. A hydraulic circuit for causing reciprocasing having first, second.third and fourth depressions separated by portions adapted to engage theseparations between ports, the second and third depressions being eachof a length to straddle a pair of adjacent ports and the separationbetween the second and third depressions being substantially wider thanthat between the first and second and third and fourth depressions, aconnection through the body of the spool valve from the first to thethird depression. and conduits leading from a fluid pressure source tothe flrst port, from the second port to one end of the cylinder, fromthe third port to the sump, from the fourth port through the throttle tothe other end of the cylinder, and from the fifth port directly to saidother end of the cylinder.

8. A hydraulic circuit for causing reciprocatory motion of a machineelement comprising a cylinder and piston one of which is stationary andthe other connected to said element, a source of fluid under pressure, asump, a throttle, and means for controllingthe flow of fluid to and fromthe cylinder comprising a spool valve casing having first, second,third, fourth and flfth ports sequentially arranged, the third portbeing substantially wider than the first, second and fourth ports, andthe several ports being separated one from the next, a spool valvewithin the casing having first, second, third and fourth depressionsseparated by portions adapted to engage the separations between ports,the second and third depressions being each of a length to straddle apair of adjacent ports and the separation between the second and thirddepressions being substantially wider than that between the first andsecond and third and fourth depressions, a connection through the bodyof the spool valve from the first to the third depression, and conduitsleading from a fluid pressure source to the first port, from the secondport to one end of the cylinderl from the third port to the sump, fromthe fourth port through the throttle to the other end of the cylinder,and from the fifth port directly to said other end of the cylinder,mechanical means for varying the position of the spool valve, a conduitleading to the end of the spool valve adjacent the first depression, anda valve connecting said end either to the pressure fluid source or tothe sump.

9. A hydraulic circuit for causing reciprocatory motion of a machineelement comprising a cylinder, and piston one of which is stationary andthe other connected to said element, a source of fluid under pressure, asump, a throttle, and means for controlling the flow of fluid to andfrom the cylinder comprising a spool valve casing having first, second,third, fourth and fifth ports sequentially arranged, the third portbeing substantially wider than the flrst, second and fourth ports, andthe several ports being separated one from the next, a spool valvewithin the casing having first, second, third and fourth depressionsseparated by portions adapted to engage the separations between ports,the second and third depressions being each of a length to straddle apair of adjacent ports and the separation between the second and thirddepressions being substantially wider than that between the first andsecond and third and fourth depressions, a connection through the bodyof the spool valve from the first to the third depression, and conduitsleading from a fluid pressure source to the ilrst port, from the secondport to one end of the cylinder, from the third port to the sump, fromthe fourth port through the throttle to the other end of the cylinder,and from the fifth port directly to said other end of the cylinder,mechanical means for varying the position of the spool valve, a conduitleading to the end' o1' the spool valve adjacent the first depression, avalve connecting said end either to the pressure uid source or to thesump, andvspring means normally holding said last-named valve in aposi-4 tion connecting the end of the spool valve to the sump.

10. A hydraulically operated machine tool comprising a reciprocableelement, a cylinder and a piston one of which is stationary and theother of which is connected to said element, a source of liquid underpressure, a. sump, a throttle, a valve including a casingand a recip-.rocable spool therein projecting from the casing at one end only, thecasing and spool being relatively formed so that in one position, inwhich the spool extends a maximum distance into the casing, the sourceis connected to one end of the cylinder and the other end of thecylinder is connected directly to the sump, in'a second position thesource is connected to one end of the cylinder and the 'other end of thecyunder is connected to the sump through the throttle, in a thirdposition the source and sump are connected together, and in a fourthposition, in which the spool extends a minimum distance into the casing,the source is connected to said other end of the cylinder and the firstend thereof is connected to the sump, mechanical means for shifting thevalve between said positions, a pilot valve normally in a positionventing to the sump the space between the casing and the 4end of thespool, movable temporarily to a position admitting pressure fluid tosaid space to shift the iirstnamed valve into its fourth position, anoperating rod for said pilot valve located at approximately the centerof travel of said element, an operating rod for mechanical shifting ofthe spool located at approximately the center of travel of said element,dogs for actuating said rods independently, and a cycle reversing valvelocated between said spool valve and the cylinder.

FRANK W. CURTIS.

